There are three riding situations in which snowmobiles are commonly used: (1) trail riding, (2) mountain riding, and (3) utility riding.
Trail riding is typically performed on packed trails, which may or may not be groomed. As the snowmobile travels over packed snow, the snowmobile skis are firmly supported by the snow. Consequently, the floatation of the ski on the snow is of little concern in trail riding. Because of this, narrow skis are preferably used for trail riding. The narrow skis enhance the quickness with which the snowmobile can be maneuvered. The narrow skis also minimize the frictional drag between the skis and the packed snow.
In contrast, mountain riding typically occurs on unpacked snow. In many instances, the unpacked snow may be quite deep. As unpacked (or powder) snow is less supportive than packed snow, snowmobiles equipped for mountain riding preferably include wide skis to enhance the floatation of skis on the snow. Specifically, skis for mountain riding typically are widened toward the inside so that extra flotation is provided to the ski. However, skis for mountain use are typically not widened toward the outside, because mountain riding requires of the snowmobile on the mountain as the snowmobile climbs the mountain. During side-hilling, the outside of the ski opposite to the direction of turning is relied upon to execute the turn. This turn maneuver is assisted by a runner, which is attached to the ski generally below the axis of rotation of the ski. Because any extra width at the outside of the ski does not benefit the ability of the ski to execute a side hill turn maneuver (but, instead hinders turning), the ski is widened only at an inside portion.
Like mountain riding, utility riding also requires that the skis on a snowmobile provide a high degree of floatation. Utility use of a snowmobile often involves the transporting of goods or people either directly on the snowmobile itself or on a trailer towed behind the snowmobile. Wide skis ensure enough floatation to the snowmobile to prevent the skis from digging into the snow under the extra weight placed on the snowmobile.
Snowmobiles equipped with skis for utility use differ from snowmobiles equipped for mountain use, because side-hilling is not relied upon to turn the vehicle. Since a utility-use snowmobile maneuvers like a trail-use snowmobile (but requires additional floatation because it travels through unpacked snow), both sides of the skis may be widened to provide as much floatation as possible.
In the prior art, there are only two ways known to alter the width of the skis on a snowmobile. The first is to install entirely new skis specifically designed for the particular use contemplated for the snowmobile. The second is to install on the bottom of the skis a product known as “skins.”
Skins are plastic attachments that are wider than typical trail skis. Skins attach to the bottom of trail skis and substantially cover the entirety of the bottom of the skis to which they are attached. Naturally, because they are designed to change the flotation capacity of the skis to which they are attached, skins are generally wider than trail skis. As attachments, skins may be designed as wide or as narrow as required for a particular type of riding condition.
Skins, however, are not easily attached to the bottom of skis. To the contrary, the runner on the bottom of the ski must be removed before the skin may be positioned against the bottom of the ski. The runner is then replaced on the ski and the ski is replaced on the snowmobile. The runners hold the skins to the skis.
Typically, skins enhance the width on both sides of the skis to which they are attached. As a result, skins are typically used only on utility snowmobiles and are not used for trail or mountain snowmobile use.
For the most part, skins are manufactured from plastic. Snowmobile riders prefer plastic because it has a relatively low coefficient of friction when moving across snow. Because of this, skins have also been created to attach to the bottom of steel skis, which have a higher coefficient of friction when traveling over snow.
To date, the prior art lacks a ski design that may be used for all three riding conditions. A need has developed for such a snowmobile ski. In particular, a demand has arisen for a ski adaptable to all three common snowmobile use situations, which are trail use, mountain use, and utility use.